Swedish physiologist who, with British biophysicist Sir Bernard Katz and American biochemist Julius Axelrod, received the 1970 Nobel Prize for Physiology or Medicine. All three were honoured for their independent study of the mechanics of nerve impulses.

Euler was the son of 1929 Nobel laureate Hans von Euler-Chelpin. After his graduation from the Karolinska Institute in Stockholm, Euler served on the faculty of the institute from 1930 to 1971. He joined the Nobel Committee for Physiology and Medicine in 1953 and was president of the Nobel Foundation for 10 years (1966–75).

Euler's outstanding achievement was his identification of noradrenaline (norepinephrine), the key neurotransmitter (or impulse carrier) in the sympathetic nervous system. He also found that norepinephrine is stored within nerve fibres themselves. These discoveries laid the foundation for Axelrod's determination of the role of the enzyme that inhibits its action, and the method of norepinephrine's reabsorption by nerve tissues. Euler also discovered the hormones known as prostaglandins (prostaglandin), which play active roles in stimulating human muscle contraction and in the regulation of the cardiovascular and nervous systems.